Boring bar guiding mechanism



Feb. 6, 1940. F. P. HEALY BORING BAR GUIDING MECHANISM Filed July 17, 1937 4 Sheets-Sheet l AToRNEYs VI M d E H W mm M m0 wm Feb. 6, .1940. F; P. HEALY BORING BAR GUIDING MECHANISM Filed July 17, 1957 4 Sheets-Sheet 2 Feb. 6, 1940. F. P. HEALY BORING BAR GUIDING MECHANISM 4 sheets-sheet 5 Filed July 17, 1937 INVENTOR f/wvc/s @f7/541.7

TTORNEYS Feb. 6, 1940.

Filed .July 17, 1937 4 sn l 9v/i] Cm 0f a //7 //3 F. P. HEALY BORING BAR GUIDING MECHANISM eets-Sheet 4 ATTORNEYS Patented Feb.l 6, 1940 UNITED STATES PATENT OFFICE l e 2,189,004 y' A" soRiNG BAR GUiDING MECiANIs'M Francis r. Healy, springfield, Mags., asigneift Van Norman Machine Tel Company, Springfield, Mass., a corporation of Massachusetts Application July 1v, 1937, serial No. 154,269` 4 claims. (o1. 77;@

This invention relates to boring devices of precision, and has particular reference to mechanism for guiding the cutter during the boring operation.

In accordance with the invention the cutter guiding devices are given an improved control over the cutter by providing them with expanding` mechanism which holds them rigidly in contact with the bore Wall until the inward pressure on the guide fingers exceeds a predetermined maximum, while ypermitting them to yield when this pressure is exceeded. By setting this limiting pressure, above that caused by the reaction of the cutting tool the latter is held rigidly under all normal conditions.

In accordance withfa further feature of the invention the cutter guiding devices are automatically controlled in accordance with the position of the boring bar in the bore. This is in part made possible by the provision of improved expanding mechanism for the cutter guiding ngers which is inherently suited to automatic control.

In accordance with a further feature of the invention the guiding of the cutterat the beginning of the boring yoperation is improved by causing the guiding iingers to contact a guiding surface external and adjacent to the bore prior to their entry into the cylinder, the guiding sur- .g face being preferably slightly larger than the bore so that the fingers will be forced to contract as they'enter the bore. l

The invention also contemplates mechanical improvement in the construction of the boring bar and in particular the construction of the cutter guiding fingers -which will be pointed out in detail below. e

Referring to the drawings, y

Fig. 1 is a vertical median section through boring spindle embodying my invention;

Fig. 2 is an enlarged section of the lower portion of the spindle with the cutter shaft and the,l

cutter-helder removed; y

Fig. 3 is a section on line 3--3 of Fig. UZ;

-Fig. 4is a sectionA on line 4-4 of Fig. v2;

Fig. 5 is a bottom. View ofY the guide finger expand-ing member shown in `'sidey elevation in Fig. 7; w y

Fig. 6 is an enlarged section of the lower portion of the spindle, with all parts but the guide iingersupporting cap removed; ,Y

Fig. 7 is a side elevation of the lower portion of the guide finger expanding member;

- Fig. 8 is a side elevation of a conventional bor- Q'f ing machine embodying my invention;

Fig. 10 is a detail, .on a larger scale, kof parts shown in` Fig. 8; ar'd 'au of' the spindles of a multiple spindle boring machine. In the present case the sleeve is shown as provided' with 'a shoulder l2 which bears against the lower side of themember Il and with a collar i3 threaded on its exterior which bears against th'eupp'er side of the'member. The detailed methodv ci securing is not important, and the sleevev andthe member ll can for practical purposes be considered as unitary. A

4 At its upper 'end the` sleeve ysupportsthe outer race I4 of arf-aller bearing l5 of the conical type serving tor carry bothradial load and axial thrust. The inner race I6 of this bearing'xsupports the upper end of a cutter shaft Il revolving freely inside of the sleeve. At it`s lower end the sleeve lo'earingisA 'carried bya 4cutterrholder 25 fitted onto a taper 26 formedfo'n the lower end of the shaft Il 'and ysecuri-d ,thereon as by threads 2l. The lower side o f theV 'cutter holder is open for vconvenience in manufacture and is closed by a plate 28 forminghonevwall o f a radial slot 29 in which a cutter '.'i 'may be inserted. This cutter is of the extensible type fully described in the Arp Patent 1,906,241, 2, 1933, and when set to a predetermined Yoverall length outside of the cutter head is' inserted in the slot so that itsv inner end rests against a stop'3l which, while adjustable, normally remains in a iixed position. The operation-and manner of setting of this cutter is fully set forth in the Arp patent and need` not be further considered here. An oil packing r32 ofanyvdesired design is preferably located 'between the bearing 23 and the cutter lhead to prevent leakage of oil.

Above and resting against the inner 'mee It of the upper shaft bearing l5vis a pinion 35 keyed.-

toV the shaft at 36 y'and convenientlyserving as a connection to any desired source of power by' which thekshaft may bertated. lIt will be understood thatwtheshaft is., rotated in timed relation t'o the yreciprocatory movement 'of the member IlV so that the cutter describes a helical path through the cylinder to be bored. A washer 31 rests on the pinion, and a heavy spring 38 is compressed between this washer and a collar 39 threaded onto the shaft at lli and held in adjusted position by a set screw di. This compression spring acts to draw the shaft |I upwardly with respect to the sleeve i5 to the extent permitted by the bearings l5 and 23, preloading these bearings sufficiently to prevent any lateral movement of the shaft with respect to the sleeve.

In aligned slots 45 and 45 (Fig. 3) formed in the sleeve I@ and the shouldered part I9 of the cap i8 respectively slide a plurality of guide iingers or cats-paws 47. In the case shown there are four sets of slots and four guide fingers spaced equally around the periphery of the sleeve. Each finger is preferably beveled on its lower outside edge as at t8 for a purpose to be described. The vinner ends of the guide fingers are likewise beveled at 50 for contact with portions 5| of a cone 52. The portions 5| may be flattened as shown or may be left as a part of the conical surface. The particular relationship of the cone to the fingers will be considered at length below. Each finger is held in contact with the cone by a spring 53 located in a recess 54 in the lower part of the finger and pressing against a pin 55 secured to the cap I8.

The cone member 52 is provided with a key way 60 in which ts a pin 6| secured to the sleeve ID to prevent the cone from. rotating while permiting it to move axially. The cone is threaded at 62 to a tube 63 extending between the sleeve ID and the shaft and free from each. At its upper end the tube is threaded at 64 to a sleeve '65 having a keyway 65 in which ts a pin 61 secured to the sleeve I0. A spring 68 rests against the shouldered upper end of the sleeve 65 and is held under compression by a` collar B9 threaded into the interior of the sleeve Hl. An oil packing 7|] is preferably positioned within a recess in the upper side of the sleeve 65 to prevent oil from the bearing l5 from running down the space between the tube Hl and the shaft A shaft is journaled in the member and passes through a hole 'i2 in the sleeve i0, the hole I2 being preferably made larger than the shaft so as to avoid difficulty in assembly. The inner end of the shaft 1| has an eccentric portion 'i3 fitting loosely in a slot 'I4 formed in the sleeve 65. The shaft is provided with means, later to be described, by which it may be rotated to bring the eccentric 'I3 either into a position in which it compresses the spring G8 or into the position shown in Fig. 1 in which the eccentric is lowered sufficiently to release the spring and permit it to force the cone member downwardly. The slot is made deep enough so that in the latter position of the eccentric the spring will be resisted by the contact of the guide fingers 41 with the bore and not by contact of the upper portion of the slot with the eccentric.

Before considering the manner in which the device is controlled, the operation of the parts already described will be dealt with more fully since various novel functions are attained. In prior devices the guide fingers have been made wholly non-yielding, or have been made nonyielding inwardly but provided with a spring take-up to permit them to move outwardly as dust and chips cleared from between the guide fingers and the bore wall. Neither of these methods of mounting are entirely suited for automatic operation. Non-yielding guide fingers, if not provided with a spring take-up, may be set to their fixed diameter with some of the fingers held out of contact with the bore wall by dust or chips, and the series of fingers thus left loose in the bore. Non-yielding fingers, whether or not provided with a spring take-up, are subject to injury if, for example, the cutting point of the tool 39 should break off during the boring operation, causing the guide fingers to meet a suddenly constricted portion of the bore. While wholly yielding fingers would meet the latter condition, they would also permit the reaction of the cutter to shift the axis of the boring bar, notably where the cut being taken is not concentric with the previously bored hole.

The guide finger mounting of the present invention avoids all of the difficulties of these prior devices by causing the fingers to be rigid until a predetermined load is applied and to be yielding thereafter. By suitable design the predetermined load can be taken at a point such that the reaction of the cutting tool will cause no motion of the axis of the boring bar, whereas if a constriction in the bore is encountered the fingers will contract or collapse. This novel result is accomplished by having the spring 6G act upon the fingers through the intervention of the cone 52, and permitting the spring to be free at all times to permit the fingers to move outwardly or inwardly as may be required to keep them in contact with the bore wall. If the angle of the cone were steep enough so that the angle of contact between it and the wedgeshaped ends of the guide ngers were less than the angle of repose, the wedge would become self-locking, and no inward pressure on the 1ingers would cause them to move, no mattei' how heavy this pressure might be. In accordance with the present invention the apex angle of the cone is sufficient so that the contact angle is greater than the angle of repose, and if the contact surfaces were completely frictionless the fingers would act as if spring-supported. Since these surfaces are not frictionless the pressure of the spring and the friction on the wedge surfaces combine to cause the fingers to act as if locked at low inward pressures on the fingers, and to be released for full spring support only when a predetermined inward pressure is reached. The condition of equilibrium is determined by the standard equation for the wedge in which friction is taken into account, considering for simplicity two fingers only.

P BW cos sin (or-(p) cos (a-2) where P is the pressure of the spring just necessary to keep the lingers from moving inwardly W is the pressure inwardly on each finger p is the angle of friction tan =,u where c is the coefcient of friction 2a is the apex angle of the cone This formula will be found, together with a discussion, on page of Analytical Mechanics for Engineers, by Seely and Ensign, New York, 1927. Using this formula and assuming an apex angle of 66 and a coefcient of friction of 0.25, this shows that a spring pressure of about 27 pounds will hold the lingers xed against any movement until a pressure of 50 pounds on each of two opposite ngers is reached, which has been checked closely by experiment.

The limiting condition can be varied by changing either the apex angle of the cone or the einen suean 'sf the spring. 'nederlaag-the apex anglewithoutchanging the spring increases the pressure necessary to be exerted on opposite fingers to cause them to move inwardly, or in other words increasesthe range within which the fingers-fare rigid. It also increases the effect of l a`spring of given strength after the fingers begin 'tomova but not in the saine proportion. It is possible vwith a rather low apex angle lto use a long spring without sacricing the rigidity ci the iinfg'ers under low loadsand'thus decreasing the 'st'iness' of the assembly atI loads sufficient to'jcause movement of therngvers. i

Elven though the angleof the` cone I l i be taken so blunt as to lower the locking range below the reaction pressureof the cutter, a much more stable system will result by havingv one spring Iact'on all guide` fingers than by having individual springs acting on 'each member. Assuming 4a lfrictionless cone to illustrate the point, an in-l ward pressure one ringer due to lateral i of the shaft'will be resisted by the full tion.

' ingl'y unstable.

'.op'po'sing springs 'due to the amount of deflecl For small deflections this would be very slight'anjd the cutter'h'ead would be correspond- The construction described above lends itself to the production of other novelfunctions by the yprovision of suitable control' mechanism 'about to be described. In prior devices for guiding the vcutter of a boring bar through the bore been necessary to set the guideto exactly the diameter of the bore before starting the cut or has also b'eenvnec'essary to 'make manual adjust-r ni'nt of the guiding device at the end of the strketo permit it tor be drawn back through th cut bore. These operations are not suited to modern conditions of production lbut with the type of mechanism hitherto available they have been necessary.v By use of the guide iinger vcontrol devices'described above automatic `control is for the rst time made possible, and while various types of automatic contro-l may be used one suitable form' will be set forth below.

In Fig'. 'the boring head has. been shown as mounted in a conventional type of boring machine having a vertically reciprocated head 80 and a work table iii( Power for rotatingthe shaft Il and for reciprocating 'the head V8l) is shown as being supplied through shafts 32 and l 83 respectively. The work piece t4 is shown as secured to the work table by any suitable clamps or fixtures 85. These` parts being conventional they need not be described more in detail. The shaft li which releases the sleeve S3 is shown in 8 and ll as being provided with a pinion 8S meshing with a vrack 8l 'fixed to the rod of a ypiston running in a cylinder 89. A pipe Si! rune ningA from one end of the cylinder is joined to a relief valve 9i and to sup-ply valve 92 jointly controlled by solenoids $3y 'connected vin series. The supply valve'92 is joined by a pipe 94 with a pump gS-for somejluid such as air under pressure. The Valves 9i and 92 are arranged so that when one fopenfthe otherfis shut, thesolei noids being :arranged when` actuatedto open the supply valve andto close'the relief valve, and

when released Ato yclose thesupply Yvalve and h to open the relief valve. v The other end of' the 'f5 'cylinder 89 is connected. by a pipe @t with a relief valve Sul!k and a Vsupply Valve 9S controlled Vby solenoids 99in series, the valve 98 being also connected to the pump by the pipe 94.' 'L` A suitable electrical control is providedr sothat @1Y0 the ,expansion and 'contraction of the guide 'iin'- fgers may be controlled automatically in accordance with the position of the boring bar.` To `this end ya pair 4of limit switches 'Imi and lll'l are i mounted on th'e frame oi the boring machineand 'fili are actuated respectively bywlugs ill? and m3 'adjustably mounted in ways lull on the head 86. The lug ISZ is shown' on 'aI larger scale in Fig. 10

"to illustrate a construction preferred "when'the [fingers are to be' expanded automatically arteria() they, have gone a predetermined distance lintov the bore. In thisv Case the fingers must not be expanded during their upward stroke, so that the lug I02is pivoted at IM to an adjustablejsupport H35, is held against motion in one direction by a PL2?, stop I 36, and is permitted ,to yield in the other direction by a spring IBI. On its upward stroke the lug yields, while in the other vdirection vit is rigid and closes the limit switch.

v The limit switchv H30 is vconnected to onejside 3% of the main line HQ, and is joined by a wire II I' to the coil H2 of a `circuitV breaker to be described, the circuit continuing through wires E i3 and H4 to the second side H5y of the main linie'. A wire III also connects the switch vIii with the solenoid H8 of a relay H9 which acts to shortcircuit the switch IIJB, current passing from the solenoid H8 to the contactsIZ't and I2! of a secondv circuit breaker I22', through the solenoid S9 which operates the valve i5? and 98, and finally back through the wire "I I4 to the line SI5. The parts connected with switch lo! are exactly the same and have been denotedby primed numerals.

The relays H9 and I I9' aremerely for the purpose of insuringnaY permanent lilow of current upon a momentary'depression of the switches IM or IUI. Whenvthe switch I l, for example, has been closed the current "in the coil IIS will closetherelay IIS, and since current can flow through the coil as long fas the breaker F22 re- 'mains closed the relay H9 will remain closed as long as the breaker is not affected. Upon the closure of switch I,however, current momen'- tarily flows through the coil H2 of the circuit breaker l`22uassociated withthe switchli, and willthusrelease therelay IIB which bridges the latter switch. Closure of'either switch thus acts to energize the solenoid Valves associated, with it andtodeenergize the whole circuit, including the solenoid valves, associated` with the other switch. To make thisclearer the circuit hasbeen shownv in Fig. l2 in the condition that it assumes upon gers still contracted, the lug H32 being preferably set so as to close tlr'eswitch lill), as soon as .the 75 llingers are wholly Within the bore. l During the preliminary part of the boring operation the bar is conveniently guided by a bearing adjustably held in close relation to the top of the hole to be bored.

It will be seen that in accordance with the control system just described the guide fingers will be expanded automatically into contact with the freshly cut bore just as soon as the bore has been completed sufficiently to receive the fingers. After this the cutter will be under the direct control of the guide lingers throughout the progress of the boring operation. As soon as the cutter has passed through the lower end of the bore the switch itl will be closed and the guide ngers will be contracted so that the cutter may be drawn upwardly without causing the lingers to drag over the bore during the rapid ascent of the bar. It is generally preferable to oiset the work piece somewhat from its cutting position before drawing the bar upwardly in order to space the cutter from the wall and thus to avoid scratching it.

Under certain conditions improved results may be obtained by a slightly different method of guiding the cutting during the initial part of the boring operation. For this purpose a guide member, conveniently made in the form of a ring 30 (Fig. 9) where the conformation of the work piece permits, is secured rigidly in place above the work piece in accurate alignment with the cutter axis and the lingers 4l' expanded into contact with it before the cutter comes into contact with the bore wall. A very rigid guide is thus provided which will prevent any distortion due to exing of the bar between the guide 25 and the work piece. The guide member or ring is preferably made of very slightly larger diameter than the bore to be cut, so that the cutter may revolve within it without marring its inner surface. When the guide lingers pass from the ring into the freshly cut bore they are forced to contract slightly by contact of their beveled lower surfaces with the upper edge of the bore, this being permitted by the action of the wedge cone as previously described. This manner of operation has the additional advantage that the guide lingers slide smoothly into the bore rather than being moved radially outwardly into contact with it, so that any dust or chips will not be caught between the outer ends of the fingers and the bore wall. This avoids any temporary or permanent flexing of the bar by reason of the fingers not being permitted by such a chip to expand until all of them are in full contact with the bore. The ring i3@ may be made part of a suitable work holding fixture, but is shown as being held by studs i3! to the top of the work piece. In this case it is not necessary that the lug |02 be made yielding, as the fingers may be expanded as soon as they reach the interior of the ring on the upward stroke of the bar.

If desired, the same procedure may be followed without the use of the ring, the fingers being expanded before they descend into the bore and being forced to contract into 'the bore by contact of their beveled lower surfaces. When this manner of operation is to be followed the maximum expanded diameter of the fingers should be made very slightly greater than the diameter of the bore to be cut.

I claim:

1. A boring device comprising a rotatable cutter head, means for reciprocating and rotating `the cutter head, a guide head mounted to the -rear of the cutter head for reciprocation therewith, means for holding the guide head against rotation, a plurality of guide members radially movable in the guide head, a device having positive wedge-like connection with all of the guide members for moving them simultaneously in an outwardly radial direction, a yielding pressure device for forcing the wedge device against the guide members, power means for shifting the wedge device in a direction opposite to that given to the wedge device by the yielding pressure device, and control means for the power means including a trip operable at a predetermined point in the reciproc'atory motion of the cutter head.

2. A boring device comprising a rotatable cutter head, means for reciprocating and rotating the cutter head, a guide head mounted to the rear of the cutter head for reciprocation therewith, means for holding the guide head against rotation, a plurality of guide members radially movable in the guide head, a device having positive wedge-like connection with all of the guide members for moving them simultaneously in an outwardly radial direction, a yielding pressure device for forcing the wedge device against the guide members, the angle of the wedge being such as to prevent slippage relative to the members and thus make it irreversible in action under the normal thrust exerted upon the guide members by the pressure oi the cutter in the bore but reversible to permit slippage relative to the members and thus permit inward movement of the members against the force of the yielding pressure device under conditions of overload, power means for shifting the wedge device in a direction opposite to that given to the wedge device by the yielding pressure device, and control means for the power means including a trip operable at a predetermined point in the reciprocatory motion of the cutter head. l

3. A boring device comprising a rotatable cutter head, means for reciprocating and rotating the cutter head, a guide head mounted to the rear of the cutter head for reciprocation therewith, means for holding the guide head against rotation, a pltuality of guide members radially movable in the guide head, a device having positive wedge-like connection with all of the guide members for moving them simultaneously in an outwardly radial direction, a spring pressing against the wedge device in a direction to cause it to force the guide members outwardly, power means for shifting the wedge device in the opposite direction against the force of the spring, and control means for said power means including a trip operable at a predetermined point in the reciprocating motion of the cutter head.

ll. A boring device comprising a rotating cutter shaft, a cutter carried thereby, a circumferential series of guide members guided for radial movement in position to follow the cutter through the bore, a device having wedge Contact with the guide members for moving them radially outwardly, yielding means common tov all the guide members for causing relative movement between said device and said guide members in a direction to cause said series of guide members to be expanded by wedge action, means for controlling the operation of said yielding means during the rotation ofthe cutter shaft, and means for actuating said controlling means including a trip operable at a predetermined point in the reciprocatory motion of the cutter head.

FRANCIS P. HEALY. 

